Polyester/low-viscosity polyethylene melt blends for powder adhesives or powder coating materials and process for making same

ABSTRACT

Semi-crystalline polyester/low viscosity polyethylene melt blends, which are non-tacky and non-blocking and are more readily grindable by cryogenic grinding techniques, for providing powders suitable for powder adhesives particularly useful for fusible interlinings or for providing powder coating materials; and to the process for making the powder.

BACKGROUND

The present invention is directed to semi-crystalline polyester/lowviscosity polyethylene melt blends, which are more readily grindable bycryogenic grinding techniques to provide powders that are suitable forpowder adhesives or powder coating materials, the powder adhesives beingparticularly suitable for fusible-interlinings; and to a process formaking the powder.

Certain semi-crystalline polyesters are useful as fusible interliningadhesives and as powder coating materials. Cryogenic grinding of thepolyesters into powder and subsequent powder classification isrelatively expensive because of the difficulty in grinding them intopowders.

A fusible interlining is a fabric which has been coated on one side witha discontinuous pattern of fusible adhesive. When the interlining isbonded to a base fabric in a garment, it provides body and shape to thegarment without impairing the ability of the fabric to breathe. Fusibleinterlinings are used in the manufacture of men's and women's suits, inshirt collars and cuffs, and in the waistbands of trousers.

Certain polyamide terpolymers are currently being used as fusibleinterlining adhesives. The polymers used are generally terpolymerscontaining nylon 6, 66, and nylon 10, 11, or 12 units in the terpolymer.These polymers generally melt at about 100° C. and are used in the formof fine powders. Although used commercially, these polyamide powdershave certain deficiencies. For example, polyamides absorb large amountsof moisture and they block in the presence of high relative humidityconditions. Therefore, they must be stored in polyethylene lined bagsprior to being used.

Polyamides also have inadequate bond strength on rainwear fabrics, andthey tend to strike through on dark fabrics giving them an undesirableappearance.

Certain copolyesters are potentially useful for fusible interliningsapplications which do have adequate bond strength on rainwear fabricsand which do not tend to strike through on dark fabrics, but powderingof these copolyesters by cryogenic grinding techniques is relativelyexpensive.

It has now been found that melt blending of small amounts oflow-viscosity polyethylenes with these polyesters or copolyestersresults in substantially improved grinding rates and, therefore,substantially decreases the cost of manufacturing powder. These meltblends were found to provide non-tacky and non-blocking blends, readilyreduced to powder by cryogenic grinding techniques. The yields of powderwere also found to be substantially higher than those obtained whengrinding the non-blended polyester or copolyester.

Such low viscosity polyethylene useful in the practice of this inventioninclude both low- and high-density polyethylene materials. Suchpolyethylenes may also be unmodified or chemically modified by oxidationor grafting.

Polyesters or copolyesters useful in this invention include materialshaving melting points in the range of about 80°-175° C. with inherentviscosities of about 0.4 to 1.2.

An object of the invention, therefore, is to provide polyester/low- andhigh-density polyethylene melt blends, which are more readily grindableby cryogenic grinding techniques, for providing powders which are usefulas adhesives or powder coating materials.

Another object of the invention is to provide an economical method forobtaining polyester/low- and high-density polyethylene melt blendpowders which are particularly useful as fusible interlining adhesivesfor use in rainwear,, men's and women's suits, shirts, and trousers.

SUMMARY OF THE INVENTION

The invention is directed to semi-crystalline polyester/low viscositypolyethylene melt blends, which comprise an intimate melt blend of asemicrystalline polyester having an inherent viscosity ranging fromabout 0.4 to 1.2, a melting point of about 80°-175° C. and an apparentheat of fusion (ΔH_(f)) of ≦10 calories per gram, and a low molecularweight polyethylene having a melt viscosity ranging from about 50 to30,000 centipoises at 150° C., a density at 25° C. of about 0.90 to0.980, and an acid number of about 0-80. The low molecular weightpolyethylene is present in the blend in concentrations ranging fromabout 3 to about 30% by weight, with preferred concentrations beingabout 5 to 15 weight percent.

The "apparent heat of fusion" (ΔH_(f)) of polymers is the amount of heatabsorbed when crystallizable polymers are melted. ΔH_(f) values arereadily obtained using thermal analysis instruments, such as thePerkin-Elmer DSC-2 Differential Scanning Calorimeter or the Du PontModel 990 Thermal Analyzer with different scanning calorimeter cell. Onemethod for determining ΔH_(f) is described in the Journal of AppliedPolymer Science, 20, 1209 (1976). Measurement of ΔH_(f) is alsodescribed in Du Pont Thermal Analysis Bulletin No. 900-8 (1965).Qualitatively, it is possible to compare the degree of crystallinity ofpolymers by comparing their ΔH_(f) values.

It has been found that ΔH_(f) is an important property which has asignificant effect on grindability. When ΔH_(f) exceeds about 10calories per gram, the grindability of the polymer is adverselyaffected.

As mentioned above, the polyesters involved are of semi-crystallinenature, having apparent heats of fusion values of equal to or less than10 calories per gram. The polyethylene involved is of low viscosity,i.e., of low molecular weight, and as such may be of low or highdensity.

The percentage of polyethylene melt blended with the semi-crystallinepolyester does not affect the adhesive function of the polyester, butdoes serve to render the polyester non-blocking and non-tacky and tofacilitate grinding of the polyester from pellets or the like form intopowder materials. The mechanism by which such improved grindability isobtained is not understood. It is theorized, however, that thepolyethylene, which is substantially non-compatible with the polyester,forms sites along which cleavage planes may be formed in the pellet,thus enabling easier grinding of the pellet into powder.

More specifically, the polyester polymer may be derived from about 80-60mole percent terephthalic acid, 20-40 mole percent adipic acid, 80-60mole percent ethylene glycol and 20-40 mole percent 1,4-butanediol; andpreferably the polyester polymer may be derived from about 70 molepercent terephthalic acid, 30 mole percent adipic acid, 73 mole percentethylene glycol, and 27 mole percent 1,4-butanediol.

The polyester polymer may also be derived from 10-35 mole percentisophthalic acid, 90-65 mole percent terephthalic acid and 100 molepercent 1,6-hexanediol with preferred embodiments being derived from 10mole percent isophthalic acid, 90 mole percent terephthalic acid, and100 mole percent 1,6-hexanediol having a melting point of about 140° C.and an apparent heat of fusion of about 8 calories per gram; 20 molepercent isophthalic acid, 80 mole percent terephthalic acid and 100 molepercent 1,6-hexanediol having a melting point of about 125° C. and anapparent heat of fusion of about 5 calories per gram; and 35 molepercent isophthalic acid, 65 mole percent terephthalic acid and 100 molepercent 1,6-hexanediol having a melting point of about 140° C. and anapparent heat of fusion of about 2 calories per gram.

The polyester polymer may further be derived from 40-60 mole percentisophthalic acid, 60-40 mole percent terephthalic acid and 100 molepercent 1,4-butanediol with preferred embodiments being derived from 40mole percent isophthalic acid, 60 mole percent terephthalic acid and 100mole percent 1,4-butanediol having a melting point of about 140° C.; 50mole percent isophthalic acid, 50 mole percent terephthalic acid and 100mole percent 1,4-butanediol having a melting point of about 129° C. andan apparent heat of fusion of about 2 calories per gram; and 60 molepercent isophthalic acid, 40 mole percent terephthalic acid and 100 molepercent 1,4-butanediol having a melting point of about 140° C.

The polyester polymer may still further be derived from 70-50 molepercent isophthalic acid, 30-50 mole percent terephthalic acid, and 100mole percent 1,4-cyclohexanedimethanol, with a preferred embodimentbeing derived from 60 mole percent isophthalic acid, 40 mole percentterephthalic acid, and 100 mole percent 1,4-cyclohexanedimethanol. Thesepolyesters are substantially amorphous having apparent heats of fusionof about 1-4 calories per gram. In the preferred embodiment, theapparent heat of fusion is about 1 calorie per gram, and it has a weakmelting endotherm at 175° C.

The invention is also directed to a process by which the improvedpolyester powder adhesive described above may be produced. The processinvolves melt blending particulate or pelleted material selected from asemicrystalline polyester having an inherent viscosity ranging fromabout 0.4 to 1.2, a melting point of about 80°-175° C. and an apparentheat of fusion of ≦10, and a low molecular weight polyethylene having amelt viscosity ranging from about 50 to 30,000 centipoises at 150° C., amelting point of about 90°-135° C., a density at 25° C. of about 0.90 to0.980, and an acid number of about 0-80. The low molecular weightpolyethylene present in the melt blend is in concentrations ranging fromabout 3 to about 30% by weight. The blended materials are melt extrudedat a temperature of about 150°-250° C. into a cooling medium to form apredetermined extruded shape, which is chopped into pellets or otherwisegranulated. Then the pellets or granulated materials are ground undercryogenic temperature conditions into a powder. The semi-crystallinepolyester and low molecular weight polyethylene may be selected from thematerials described above in the description of the product.

The "cooling medium" mentioned in the preceding paragraph is generallywater having a temperature of about 5° C. to about 50° C.

The melt-extruded pellets or granulated material may also, in somecases, prior to the step of grinding, be heat treated in hot water at atemperature of about 60°-100° C. for about 10 minutes to 3 hours, andthen dried at a temperature of about 30°-80° C. for a time sufficient toremove the moisture. This heat treatment tends to increase slightly thedegree of crystallinity of the pellets or granulated material.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The blends discussed above in the "Summary of the Invention" are readilyprepared by melt blending in extruders, Brabender Plastographs, Banburymixers, and the like. The blends are readily ground in conventionalhammer mills using liquid nitrogen to cool them. High yields of powderare achieved with very low nitrogen usage. For example, the amount ofnitrogen required may be as low as about one pound of liquid nitrogenper pound of powdered product.

Powders for powder coating applications are generally less than 70 meshor less than 140 mesh materials.

Powders used for fusible interlining applications are generally appliedfrom powder point applicators, from random sprinkling equipment, or inthe form of a paste. The particle size required for each of these threetypes of applications, however, is generally quite critical. Forexample, in the application of powders from the powder pointapplicators, it is desirable to have powders with a particle size rangeof 50-200 microns (270-70 mesh). For random sprinkling application ontightly woven or nonwoven fabrics, a particle size range of 150-300micron (100-50 mesh) is desirable. For random sprinkling on an openweave fabric such as inexpensive rayon/cottons blends, powders with300-500 micron size (50-35 mesh) are required. For application of powderin paste form, it is necessary to have very fine powders. For example,in paste form, powder size should be 0-80 micron (less than 200 U.S.mesh).

"I.V." as used herein means "inherent viscosity", which is determinedusing a polymer concentration of 0.5% in the solvent (60% by weightphenol and 40% by weight tetrachloroethane). The polymer is dissolved inthe solvent at a temperature of 125° C., and I.V. is measured at atemperature of 25° C.

The following examples are intended to illustrate the invention, butshould not be understood as limiting the scope of the invention.

EXAMPLE 1

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (90 g.; I.V.[inherent viscosity] 0.73; Tm [melting point] 127° C.; ΔH_(f) 4 caloriesper gram) and oxidized, low-viscosity, high-density polyethylene (10 g.;acid No. 16; melt viscosity 160 cp. [centipoises] at 150° C.) arephysically blended and extruded at 205° C. and 150 rpm into 23° C. waterand chopped into 1/4 inch pellets. These pellets (10 g.) arecryogenically ground in a micromill and sieved through a 70 mesh screen.The blend has a grindability rating of 28.6% (percentage of powder whichwill pass through a 70 mesh screen) as compared to 10% for the polyesterwithout the blended polyethylene. The grindability rating of the blendis further improved by heat treating the pellets in boiling water fortwo hours. After drying the pellets in a vacuum oven for 16 hours at 60°C., the pellets have a grindability rating of 43%.

The cryogenically ground blend powder (<70 mesh) is applied to fusibleinterlining fabric by a random sprinkling technique and fused under anultraviolet lamp to provide a coating weight of 15 g./yard². Samples ofthe fusible interlining are bonded to polyester doubleknit fabric at152° C./4.5 psi/15 second dwell time. The peel strength of the bond is1.5 pounds/inch.

Similarly good results are obtained when the <70 mesh powder is appliedto fusible interlining fabric from a powder point coater and the dots ofadhesive are fused by passing the fabric under a bank of quartz infraredheaters.

EXAMPLE 2

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (90 g.; I.V.[inherent viscosity] 0.73; Tm [melting point] 127° C.; ΔH_(f) 4 caloriesper gram) and low-viscosity, high-density polyethylene (10 g.; meltviscosity 450 cp. at 125° C.) are physically blended and extruded at205° C. and 150 rpm into 23° C. water and chopped into 1/4 inch pellets.The grindability procedure of Example 1 is repeated and the resultingblend has a grindability rating of 17.5% as compared to 10% for thepolyester without the blended polyethylene.

EXAMPLE 3

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (90 g.; I.V.[inherent viscosity] 0.73; Tm [melting point] 127° C.; ΔH_(f) 4 caloriesper gram) and oxidized low-viscosity, low-density polyethylene (10 g.;acid No. 15; melt viscosity 1200 cp. at 125° C.) are physically blendedand extruded at 205° C. and 150 rpm into 23° C. water and chopped into1/4 inch pellets. The grindability procedure of Example 1 is repeatedand the resulting blend has a grindability rating of 34% as compared to10% for the polyester without the blended polyethylene.

Similar improvements in grindability are achieved when 3%, 5%, and 20%concentrations of the polyethylene are melt blended with the modifiedpolyester.

Samples of <70 mesh powder obtained from the 90/10polyester/polyethylene blend are coated with 0.35% Cab-O-Sil (a fumedsilica). This powder is applied to fusible interlining fabric using apowder point applicator with heated roll at 400° F., engraved roll at125° F., fusion temperature in the sintering oven controlled with Variacsetting of 160 and roll speed of 12 rpm. Fusible interlining sampleshaving a coating weight of 18 g./yard² are bonded to polyester/woolworsted fabric at 150° C./4.5 psi/15 second dwell time and the bondedsamples have a peel strength of 1.2 pounds/inch.

EXAMPLE 4

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (90 g.; I.V.[inherent viscosity] 0.73; Tm [melting point] 127° C.; ΔH_(f) 4 caloriesper gram) and low-viscosity, low-density polyethylene (10 g.; meltviscosity 1800 cp. at 125° C.) are physically blended and extruded at205° C. and 150 rpm into 23° C. water and chopped into 1/4 inch pellets.The grindability procedure of Example 1 is repeated and the modifiedpolyester/polyethylene blend has a grindability rating of 24% ascompared to 10% for the polyester without the blended polyethylene.

EXAMPLE 5

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (90 g.; I.V.[inherent viscosity] 0.73; Tm [melting point] 127° C.; ΔH_(f) 4 caloriesper gram) and maleated, low-viscosity, low-density polyethylene (10 g.;saponification No. 5; melt viscosity 12,000 cp. at 150° C.) arephysically blended and extruded at 205° C. and 150 rpm into 23° C. waterand chopped into 1/4 inch pellets. The grindability procedure of Example1 is repeated and the resulting blend has a grindability rating of 23%as compared to 10% for the polyester without the blended polyethylene.

EXAMPLE 6

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (90 g.; I.V.[inherent viscosity] 0.73; Tm [melting point] 127° C.; ΔH_(f) 4 caloriesper gram) and low-viscosity, low-density polyethylene (10 g.; meltviscosity 9400 cp. at 150° C.) are physically blended and extruded at205° C. and 150 rpm. into 23° C. water and chopped into 1/4 inchpellets. The grindability procedure of Example 1 is repeated and theresulting blend has a grindability rating of 23% as compared to 10% forthe polyester without the blended polyethylene.

EXAMPLE 7

Pellets of poly(ethylene terephthalate) polyester modified with 30 molepercent adipic acid and 27 mole percent 1,4-butanediol (I.V. [inherentviscosity] 0.79; 142 g.) and high molecular weight polyethylene (meltindex 6.4; 35.5 g.; density 0.917) are physically blended, driedovernight at 75° C. under vacuum, and melt blended in an extruder at200° C. according to the procedure of Example 1. These pellets (10 g.)are cryogenically ground in a micromill and sieved through a 70 meshscreen. This blend has a grindability rating of 12%.

Similar results are obtained when high molecular weight, high densitypolyethylene (melt index 32.7, density 0.953) is used instead of lowdensity polyethylene. This example shows that high molecular weightpolyethylenes are not useful in increasing the grindability of thepolyester.

EXAMPLE 8

Pellets of poly(hexamethylene terephthalate) modified with 10 molepercent isophthalic acid (95 g.; I.V. [inherent viscosity] 0.61; Tm[melting point] 140° C., ΔH_(f) [apparent heat of fusion] 8 cal/g.) and5 g. of low density polyethylene (melt viscosity 9400 cp. at 150° C., Tm[melting point] 100° C.) are physically blended and extruded at 205° C.and 150 rpm as a rod into 23° C. water and chopped into 1/4 inchpellets. The grindability procedure of Example 1 is repeated and thispolyester/polyethylene blend has a grindability rating of 29% ascompared to 11% for the unblended polyester.

Similarly good results are achieved when poly(hexamethyleneterephthalate) modified with 20 mole percent isophthalic acid (I.V.[inherent viscosity] 0.57; Tm [melting point] 125° C.; ΔH_(f) 5 cal./g.) or modified with 35 mole percent isophthalic acid (I.V. [inherentviscosity] 0.44; Tm [melting point] 140° C.; ΔH_(f) 2 cal./g.) are usedinstead of the poly(hexamethylene terephthalate) modified with 10 molepercent isophthalic acid.

EXAMPLE 9

Pellets of poly(tetramethylene terephthalate) modified with 50 molepercent isophthalic acid (90 g.; I.V. [inherent viscosity] 0.64; Tm[melting point] 129° C.; ΔH_(f) 2 cal./g.) and 10 g. of oxidized,low-viscosity, high-density polyethylene (acid No. 16; melt viscosity160 cp. at 150° C.; Tm [melting point] 116° C.) are physically blendedand extruded at 180° C. and 150 rpm as a rod into chilled water (18° C.)and chopped into 1/4 inch pellets. The grindability procedure of Example1 is repeated and this polyester/polyethylene blend has a grindabilityrating of 35% as compared to 14% for the unblended copolyester.

Similarly good results are achieved when poly(tetramethyleneterephthalate) modified with 40 mole percent isophthalic acid (I.V.[inherent viscosity] 0.97; Tm [melting point] 140° C.) or modified with60 mole percent isophthalic acid (I.V. [inherent viscosity] 0.81; Tm[melting point] 139° C.) are used instead of poly(tetramethyleneterephthalate) modified with 50 mole percent isophthalic acid.

EXAMPLE 10

Pellets of poly(hexamethylene terephthalate) modified with 20 molepercent 1,4-butanediol (90 g.; [inherent viscosity] I.V. 0.72; Tm[melting point] 125° C.; ΔH_(f) 8 cal./g.) and 10 g. of oxidized,low-viscosity, high-density polyethylene (acid No. 16; melt viscosity160 cp. at 150° C.; Tm [melting point] 116° C.) are physically blendedand extruded at 200° C. and 150 rpm as a rod into 23° C. water andchopped into 1/4 inch pellets. The grindability procedure of Example 1is repeated and this copolyester/polyethylene blend has a grindabilityrating of 11% as compared to 5% for the unblended copolyester.

Similarly good results are achieved when poly(hexamethyleneterephthalate) modified with 20 mole percent isophthalic acid and 20mole percent 1,4-butanediol (I.V. [inherent viscosity] 0.70; Tm [meltingpoint] 100° C.; ΔH_(f) 4 calories per gram) is used instead of thepoly(hexamethylene terephthalate) modified with 20 mole percent1,4-butanediol.

EXAMPLE 11

Pellets of poly(1,4-cyclohexylenedimethylene isophthalate) modified with40 mole percent terephthalic acid (I.V. [inherent viscosity] 0.49;ΔH_(f) 1 calorie per gram; 90 g.) and oxidized, low-viscosity,high-density polyethylene (acid No. 16; melt viscosity 160 cp. at 150°C.; 10 g.) are physically blended and extruded at 205° C. and 150 rpminto 23° C. water and chopped into 1/4 inch pellets. These pellets (10g.) are cryogenically ground in a micromill and sieved through a 70 meshscreen. The blend has a grindability rating of 35.0% (percentage ofpowder which will pass through a 70 mesh screen) as compared to 16.3%for the polyester without the blended polyethylene. This material isparticularly suitable for powder coating use.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

We claim:
 1. An improved polyester suitable for powder adhesives andpowder coating materials comprising an intimate melt blend of (A) asemicrystalline polyester having an inherent viscosity ranging fromabout 0.4 to 1.2, a melting point of about 80°-175° C. and an apparentheat of fusion of ≦10 calories per gram selected from the groupconsisting of (1) copolyester containing from 80 to 60 mole percentterephthalic acid, 20 to 40 mole percent adipic acid, 80 to 60 molepercent ethylene glycol and 20 to 40 mole percent 1,4-butanediol; (2)copolyester containing from 10 to 35 mole percent isophthalic acid, 90to 65 mole percent terephthalic acid and 100 mole percent1,6-hexanediol; and (3) copolyester containing from 40 to 60 molepercent isophthalic acid, 60 to 40 mole percent terephthalic acid and100 mole percent 1,4-butanediol; and (B) a low molecular weightpolyethylene having a melt viscosity ranging from about 50 to 30,000centipoises at 150° C., a density at 25° C. of about 0.90 to 0.98 and anacid number of about 0-80; wherein said low molecular weightpolyethylene is present in the blend in an amount of from about 3 toabout 30% by weight.
 2. An improved polyester powder as defined in claim1, wherein the polyester is derived from about 70 mole percentterephthalic acid, 30 mole percent adipic acid, 73 mole percent ethyleneglycol, and 27 mole percent 1,4-butanediol.
 3. An improved polyesterpowder as defined in claim 1, wherein the polyester is derived from10-35 mole percent isophthalic acid, 90-65 mole percent terephthalicacid, and 100 mole percent 1,6-hexanediol.
 4. An improved polyesterpowder as defined in claim 3, wherein the polyester has a melting pointof about 140° C. and an apparent heat of fusion of about 8 calories pergram and is derived from 10 mole percent isophthalic acid, 90 molepercent terephthalic acid, and 100 mole percent 1,6-hexanediol.
 5. Animproved polyester powder as defined in claim 3, wherein the polyesterhas a melting point of about 125° C. and an apparent heat of fusion ofabout 5 calories per gram and is derived from 20 mole percentisophthalic acid, 80 mole percent terephthalic acid, and 100 molepercent 1,6-hexanediol.
 6. An improved polyester powder as defined inclaim 3, wherein the polyester has a melting point of about 140° C., andan apparent heat of fusion of about 2 calories per gram and is derivedfrom 35 mole percent isophthalic acid, 65 mole percent terephthalicacid, and 100 mole percent 1,6-hexanediol.
 7. An improved polyesterpowder as defined in claim 1, wherein the polyester is derived from40-60 mole percent isophthalic acid, 60-40 mole percent terephthalicacid, and 100 mole percent 1,4-butanediol.
 8. An improved polyesterpowder as defined in claim 7, wherein the polyester has a melting pointof about 140° C. and an apparent heat of fusion of about 2 calories pergram and is derived from 40 mole percent isophthalic acid, 60 molepercent terephthalic acid, and 100 mole percent 1,4-butanediol.
 9. Animproved polyester powder as defined in claim 7, wherein the polyesterhas a melting point of about 129° C. and an apparent heat of fusion ofabout 2 calories per gram and is derived from 50 mole percentisophthalic acid, 50 mole percent terephthalic acid, and 100 molepercent 1,4-butanediol.
 10. An improved polyester powder as defined inclaim 7 wherein the polyester has a melting point of about 140° C. andan apparent heat of fusion of about 2 calories per gram and is derivedfrom 60 mole percent isophthalic acid, 40 mole percent terephthalicacid, and 100 mole percent 1,4-butanediol.
 11. An improved polyesterpowder as defined in claim 1, wherein the low molecular weightpolyethylene is present in the blend in an amount of from about 5 toabout 15% by weight.
 12. A process for producing an improved polyesterpowder suitable for powder adhesives and powder coating materials, theprocess comprising:melt blending particulate or pelleted materialselected from a semicrystalline polyester having an inherent viscosityranging from about 0.4 to 1.2, a melting point of about 80°-175° C. andan apparent heat of fusion of ≦10, and a low molecular weightpolyethylene having a melt viscosity ranging from about 50 to 30,000centipoises at 150° C., a melting point of about 90°-135° C., a densityat 25° C. of about 0.90 to 0.980, and an acid number of about 0-80; thelow molecular weight polyethylene being present in the blend inconcentrations ranging from about 3 to about 30% by weight; meltextruding the blended materials at a temperature of about 150°-250° C.into a cooling medium to form a predetermined extruded shape; formingthe extruded shape into pellets or granulated materials; and grindingsaid pellets or granulated materials under cryogenic temperatureconditions into said powder.
 13. A process as defined in claim 12,wherein the cooling medium is water having a temperature of about 5°C.-50° C.
 14. A process as defined in claim 12 wherein the pellets orgranulated materials, prior to the step of grinding, are heat treated inhot water at a temperature of about 60°-100° C. for about 10 minutes to3 hours and dried at a temperature of about 30°-80° C. for a timesufficient to remove the moisture.
 15. A process as defined in claim 12,wherein the polyester is derived from about 80-60 mole percentterephthalic acid, 20-40 mole percent adipic acid, 80-60 percentethylene glycol and 20-40 mole percent 1,4-butanediol.
 16. A process asdefined in claim 15, wherein the polyester is derived from about 70 molepercent terephthalic acid, 30 mole percent adipic acid, 73 mole percentethylene glycol, and 27 mole percent 1,4-butanediol.
 17. A process asdefined in claim 12, wherein the polyester is derived from 10-35 molepercent isophthalic acid, 90-65 mole percent terephthalic acid, and 100mole percent 1,6-hexanediol.
 18. A process as defined in claim 17,wherein the polyester has a melting point of about 140° C. and anapparent heat of fusion of about 8 calories per gram and is derived from10 mole percent isophtalic acid, 90 mole percent terephthalic acid, and100 mole percent 1,6-hexanediol.
 19. A process as defined in claim 17,wherein the polyester has a melting point of about 125° C. and anapparent heat of fusion of about 5 calories per gram and is derived from20 mole percent isophthalic acid, 80 mole percent terephthalic acid, and100 mole percent 1,6-hexanediol.
 20. A process as defined in claim 17,wherein the polyester has a melting point of about 140° C., and anapparent heat of fusion of about 2 calories per gram and is derived from35 mole percent isophthalic acid, 65 mole percent terephthalic acid, and100 mole percent 1,6-hexanediol.
 21. A process as defined in claim 12,wherein the polyester is derived from 40-60 mole percent isophthalicacid, 60-40 mole percent terephthalic acid, and 100 mole percent1,4-butanediol.
 22. A process as defined in claim 21, wherein thepolyester has a melting point of about 140° C. and an apparent heat offusion of about 2 calories per gram and is derived from 40 mole percentisophthalic acid, 60 mole percent terephthalic acid, and 100 molepercent 1,4-butanediol.
 23. A process as defined in claim 21, whereinthe polyester has a melting point of about 129° C. and an apparent heatof fusion of about 2 calories per gram and is derived from 50 molepercent isophthalic acid, 50 mole percent terephthalic acid, and 100percent 1,4-butanediol.
 24. A process as defined in claim 21, whereinthe polyester has a melting point of about 140° C. and an apparent heatof fusion of about 2 calories per gram and is derived from 60 molepercent isophthalic acid, 40 mole percent terephthalic acid, and 100mole percent 1,4-butanediol.
 25. A process as defined in claim 12,wherein the polyester is derived from 60 mole percent isophthalic acid,40 mole percent terephthalic acid, and 100 mole percent1,4-cyclohexanedimethanol.
 26. A process as defined in claim 12, whereinthe concentrations of low molecular weight polyethylene blended into theblend ranges from about 5 to about 15% by weight.